It is known, in the practice of spectrophotometry and ellipsometry and the like, to direct electromagnetic radiation onto small spots on samples.
Patents to Coates Nos. 5,045,704 and RE: 34,783, for example, describe a system which applies a reflective objective lens to direct electromagnetic radiation provided to it by a convex reflective element to a spot on a sample. Said electromagnetic radiation is provided to said convex reflective element via a beam splitter. It is noted that the concave reflective objective lens disclosed in said Coates Patents is of a donut shape, which can be more difficult to manufacture than a plurality of spherical concave mirrors.
A U.S. Pat. No. 5,917,594 to Norton describes a system for providing a beam of electromagnetic radiation to a small spot on a sample utilizing a sequence of aberration correcting refractive elements, and a spherical mirror. It is noted that only incident light is passed through said aberration correcting refractive element.
Additional Patents to Norton et al. include Nos. 5,486,701 and 5,859,424, and a Patent to Piwonka-Corle et al., No. 5,608,526. Said Patents describe use of spherical reflective focusing elements to converge a beam of electromagnetic radiation into a small spot on a sample.
U.S. Pat. No. 6,744,505 B1 to Wang et al. is disclosed as it describes use of a concave reflecting optics to direct diverging diffracted electromagnetic radiation into a collimated beam which enters a detector. Further disclosed is a Published Application of Wang et al. is No. 2004/0125369 A1.
U.S. Pat. No. 3,748,015 to Offner is disclosed as it describes an imaging system comprising two elements:                a) a concave spherical mirror; and        b) a convex spherical mirror;said elements being arranged such that electromagnetic radiation caused to approach the concave spherical mirror reflects at a first location thereon and is reflected to said convex spherical mirror, from which it reflects onto a second location of said concave spherical mirror, from which it reflects as a beam of electromagnetic radiation, which, if the electromagnetic radiation caused to approach the concave spherical mirror at a first location was, for instance, an imaged aperture, appears as a small spot on the sample. It is emphasized that a collimated electromagnetic beam is not “focused” by the 1:1 imager, but rather a substantially point source is imaged thereby.        
Patents identified by the Examiner in examination of the Parent application Ser. No. 10/928,904 are:                4,650,315 to Markle;        6,835,933 to Lin et al.;        5,136;413 to NacDonald et al.;        4,688,904 to Hirose et al.;        6,141,100 to Burka et al.        
An additional clever combination of refractive and reflective optics to provide aberration corrected small spots of electromagnetic radiation onto samples would provide utility, particularly if it allowed selection of angles-of-incidence at which a beam impinges on a sample.